Tools permitting machining and/or checking without contact with a workpiece, such as laser beam machining heads, have fragile operating parts which need to be protected in the event of shock.
In the case of a laser beam machining head the operating parts are understood to mean the focussing means made up of one or more lenses located in the head and associated with a machining nozzle.
It is known that, if a head of this type is to function correctly, i.e. for the machining to be carried out efficiently, it is necessary to adjust the point of convergence of the beam, on the one hand in relation to the workpiece and, on the other hand, in relation to the orifice of the nozzle.
This adjustment is a delicate operation and is of only very moderate stability if the head strikes an obstacle. If, for example, the nozzle only strikes against the workpiece, for example because of an error in manipulating or programming the machine, this can cause misalignment of the axis of the laser beam with the orifice of the nozzle (the diameter of which is of the order of a few millimeters), thus rendering the head useless until the nozzle is readjusted in relation to the focussing means, possibly necessitating replacement of the nozzle.
As stated above, the operation of readjusting the focussing means in relation to the nozzle is delicate and has to be carried out by highly skilled personnel.
As a result, the slightest shock between the head and an obstacle involves high manpower costs on the one hand and/or material costs on the other hand.
To overcome these problems a system is known which uses shock detectors designed to stop any movement of the head in respect of the piece or frame in the event of a shock.
A system of this type is effective if the movements of the head in relation to the piece or the frame are slow, but it does not make it possible to react sufficiently quickly if the head strikes an obstacle at high speed, with the result that there is great danger of damage to the head which is rigidly associated with its support.